Advances in electronics have made it trivial to capture and edit creative digital works, including images, audio, and video. These advances also make it difficult to control unauthorized copying and alteration of these works. In particular, one challenge presented by this technology is to uniquely associate a work with its creator. Another challenge is to prevent tampering of the work, or at least provide a reliable method for detecting tampering.
One way to associate multimedia data with its owner or creator is to hide identifying information in the media signal through data hiding or steganography. Steganography refers to a process of hiding information into a signal. One example of steganography is digital watermarking. Digital watermarking is a process for modifying media content to embed a machine-readable code into the data content. The data may be modified such that the embedded code is imperceptible or nearly imperceptible to the user, yet may be detected through an automated detection process. Most commonly, digital watermarking is applied to media such as images, audio signals, and video signals. However, it may also be applied to other types of data, including documents (e.g., through line, word or character shifting), software, multi-dimensional graphics models, and surface textures of objects.
Digital watermarking systems have two primary components: an embedding component that embeds the watermark in the media content, and a reading component that detects and reads the embedded watermark. The embedding component embeds a watermark by altering data samples of the media content in the spatial, temporal or some other transform domain (e.g., Fourier, Discrete Cosine, Wavelet Transform domains). The reading component analyzes target content to detect whether a watermark is present. In applications where the watermark encodes information (e.g., a message), the reader extracts this information from the detected watermark.
The present assignee's work in steganography, data hiding and watermarking is reflected in U.S. Pat. No. 5,862,260; in application Ser. Nos. 09/503,881 and 09/452,023 (now U.S. Pat. Nos. 6,614,914 and 6,408,082); and in published specifications WO 9953428 and WO0007356 (corresponding to U.S. application Ser. Nos. 09/074,034 (now U.S. Pat. No. 6,449,377) and 09/127,502 (now U.S. Pat. No. 6,345,104)). A great many other approaches are familiar to those skilled in the art. The artisan is presumed to be familiar with the full range of literature about steganography, data hiding and watermarking.
The invention provides methods, systems and devices for capturing and encoding a user attribute in a media signal. It also provides methods, systems and devices for authenticating the media signal using the encoded user attribute data.
One aspect of the invention is a method for capturing and encoding a user attribute in a media signal. This method applies to a variety of media signals, including images (still and video) and audio. The method captures a user attribute of the user of a media signal capture device, such as a camera, video recorder, etc. It then encodes the user attribute into a media signal captured by the device. The method may be implemented in the media signal capture device, which enables the user attribute data to be captured from the user and encoded into content as it is being captured by the device.
One type of user attribute data is a retinal scan. This type of data is particularly suited for digital camera applications. In such applications, an image sensor may capture the photographer's retinal image for immediate encoding into an image captured with the same or a different image sensor in the camera. The method applies to other media capture devices, media signal types, and user attributes such as a voice signature, fingerprint, etc.
Another aspect of the invention is a media signal capture device capable of encoding a user attribute in a media signal captured in the device. The device includes a user attribute capture unit for capturing a user attribute of a user of the media signal capture device. It also includes an encoder for encoding the user attribute into a media signal captured by the device.
Another aspect of the invention is a method of authenticating a media signal. The method decodes user attribute data encoded in the media signal within a media signal capture device that captured the media signal. It then compares the decoded user attribute data with user attribute data computed for a person. This process may be used to verify that a creator of the content, such as photographer, did create the media content in question (e.g., a photograph, video recording, etc.).
Further features will become apparent with reference to the following detailed description and accompanying drawings.